Turning to Tech on the Road by SAM GROBART

LAS VEGAS — If Mercedes, BMW and Ford have their way, the new cars they build will be able to port apps, games, music and movies from a smartphone to a car’s entertainment system.

But for every potential distraction automakers add, they find themselves having to build in ways to prevent drivers from crashing their new smartphone on wheels: automatically applying the brakes at a traffic light; alerting drivers when a car is in the blind spot, or reading traffic signs and slowing a car as speed zones change.

As cars become ever more vibrant entertainment centers, automakers find themselves in a kind of arms race with themselves that they are powerless to prevent. “We can’t stop the prolific growth of consumer technology,” said Paul Mascarenas, chief technical officer at Ford. “We can’t stop people bringing phones in their cars. We endeavor to make sure people do it in the safest way possible.”

Ford’s Sync App Link, Mercedes-Benz’s forthcoming DriveStyle app and BMW ConnectedDrive have slight differences in execution, but the purpose is the same: importing apps and content from a smartphone into the car’s displays and controls.

Using the smartphone as a hub of digital content and services means drivers are able to preserve the same media and features they use when they are out of their cars. “You’re already used to using your phone,” Mr. Mascarenas said. “We’re trying to create a seamless experience from your home or office into your car.”

Adding technology that brings the online world into a car’s cockpit obviously increases the risk that a driver will become distracted. The National Transportation Safety Board has joined safety organizations in calling for bans on cellphone use while driving. The auto industry’s response is to use other technologies to try to reduce that risk.

Today’s cars already can do many automated safety tasks. They can maintain a set distance from the car in front of it and apply mild corrective steering to keep a car in its lane. They can also automatically adjust the headlights and determine if drivers are drowsy and then sound an alarm to awaken them.

Automakers acknowledge that the foundations are already in place for cars that, one day, may drive themselves. At that point, the issue of distraction is substantially reduced.

Fully autonomous cars, from research projects at Google to automakers’ own prototypes, have already proved to be viable. In 2010, driverless cars that participated in VisLab’s Intercontinental Autonomous Challenge drove about 9,300 miles from Parma, Italy, to Shanghai. That was an extreme test of autonomous-car technology, but more prosaic uses may be tried in the future.

“If you’re stuck in a traffic jam or driving hundreds of miles in a straight line across Nebraska or Montana,” Dieter Zetsche, the Mercedes-Benz chief executive, said in a speech at C.E.S. on Tuesday, “it might be better for you to read a book.”

Automakers see other benefits to letting mobile app developers add all kinds of things to cars. It may help bring down the cost of car.

“You already have a phone with things like navigation and music and local information,” said James Buczkowski, Ford’s director of electrical and electronics systems. “It’s cheaper for both consumer and for us. We don’t have to build it. We can rely on our partners.”

It can also help cars stay up to date. The typical car can require seven years or more of development. Designs and specifications are fixed years before the first vehicle rolls down the assembly line. Changes in consumer technology — where major updates to the software, if not entire new models, are released on at least an annual basis — move at a far faster rate. By making the smartphone a component of the car, automakers hope to hitch a ride on a technology that changes in months, not years.

“While we are already working on the cars that will hit the road seven years from now, the next disruptive consumer technology might hit the market in seven months,” Dr. Zetsche said. “A 20-year-old car might be a classic that you love to drive, but do you know anybody who is still using a 20-year-old mobile phone?”